1. Field of the Invention
The present invention generally relates to a method for manufacturing a semiconductor device, and more specifically, to a technology of expanding an active region and a recess region by an epitaxial growth process in order not to reduce a process margin in formation of the active region, a device isolation film and a bulb recess region due to reduction of the size of the semiconductor device.
2. Description of the Related Art
Due to high integration of semiconductor devices, the process margin for forming an active region and a device isolation film has been reduced. While the line width of a gate has become narrower and the channel length has become shorter, electric characteristics of the semiconductor device have been degraded. As a result, a recess gate has been used to prevent reduction of the channel length. The recess gate is a technique to etch a semiconductor substrate at a predetermined thickness and increase the contact area between the active region and the gate, thereby increasing the gate channel length.
Meanwhile, while the size of the semiconductor device has become smaller, there is a limit to the increase of the channel length with the recess region. Also, it is difficult to secure a subsequent landing plug contact region. As a result, a bulb recess region is formed to secure the channel length efficiently and also to secure the landing plug contact region sufficiently. However, an etching process is required to be performed twice to form the bulb recess region, and as a result, the process margin is limited.